Crane having governing means for steering the crane frame travelling along the track



y 3, 1960 NGSKOG 2,935,032

L. Tl CRANE HAVING GOVERNING MEANS FOR STEERING THE CRANE FRAME TRAVELLING ALONG THE TRACK Filed March 19, 1957 v United States Patent C CRANE HAVING GOVERNING MEANS FOR STEERING THE CRANE FRAME TRAVEL- LING ALONG THE TRACK Lennart Tingskog, Vasteras, Sweden, assignor to Allmiinna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Application March 19, 1957, Serial No. 647,073

Claims priority, application Sweden March 23, 1956 3 Claims. (Cl. 105-163) can be given a low value, the steering of the crane frame travelling along the track causes no serious problems. However, with cranes having a large span it is very often necessary to give a high value to the ratio between the span and the wheel base. A high value of the said ratio has an injurious influence on the travelling of crane frames having flanged wheels. A very serious disadvantage is that the crane frame and the rails are exposed to very heavy forces when the crane tends to depart from a straight line or when there is any variation in the distances between the rails of the track. Another disadvantage is that the force of friction will be very high and the wear on the wheel flanges and the rails will be quite heavy. Under unfavourable conditions the crane frame may twist, the rails may bend or the crane may jump off the rails. It has been heretofore proposed to use steering means connected to means indicating the angle between the crane frame and the track and to actuate the crane travelling gear in such a way that the speed of one or more of the driving wheels is changed so that the frame takes a different angular position in relation to the track. The travelling wheels have then been provided with flanges which prevented the crane frame from moving too far sideways as the steering means was only able to bring it back to a definite angular position in relation to the track, and was unable to adjust its position when it had been moved sideways from its normal position in relation to the track.

The present invention relates to a crane that travels on rails, and comprises one or more driving motors connected to driving wheels arranged on end girders of the crane frame, control means sensitive to the sidcward movement of a point in thefront part of the crane frame in relation to the crane track, and governing means connected to said control means, which means govern the speed of the driving wheels at one or both ends of the crane frame depending on the said sideways movement. The control means are guided by one of the rails of the track or by a separate guide rail. Suitable control means are arranged on both sides of the crane frame centre line perpendicular to the track. The governing means connected to the front control means affects the speed of the driving wheels only when the crane is travelling. The control means may consist of forks or rollers which are movably arranged in the crane frame over one of the track rails or over the separate guide rail. These forks or rollers follow the rail and are sensitive to the side movement of a point in the frame above them and actuate the governing means influencing the speed of the driving wheels. As only the governing means connected to the front control means influence the driving wheel speed, the crane is provided with automatic changeover means which connects the governing means to the travelling gear when the travelling starts. The changeover means may consist of a contactor connected to the travel control lever or a relay connected to a circuit in the driving device.

In order to correct the position of the crane frame in relation to the crane track by changing the speed of the driving wheels, the driving gear may be influenced in many difierent ways. The governing means may consist of a rheostat, the movable contact of which is connected to the indicating means. This rheostat can influence the current to the driving motors of the driving gear. When one track motor is connected to the driving wheels at both ends of the crane frame by countershafts, the rheostat influences the speed and the direction of rotation of a motor driving a diiferential gear arranged between the track motor and one of the driving wheels. Depending on the direction of rotation of the said motor, the speed of the wheel on the side of the track motor Where the differential gear is arranged, is lowered or increased. It is also possible to use electrically operated clutches which are operated by the governing means between the track motor and the driving wheels of the crane. When track motors are used, one at each end of the crane frame, it is possible to change the field current to one or both of the motors or to break the cur-rent supply to one of the motors for short periods.

Cranes according to the invention are provided with safety devices preventing the crane frame from jumping oif the rails if faults occur in the electric steering equipment. The wheels may be provided with flanges which do not normally come into contact with the sides of the rails. It is also possible to use, for the same purpose, horizontal guiding rollers, which do not normally come into contact with the rails. These guiding rollers may be of very simple construction as they are very seldom required to take up a force.

As a result of the invention, the side force on rails and wheels will be very low and therefore the travelling resistance and the wear on the rail sides and wheel flanges will also be low. Cranes having a large span can be made with a very small wheel base without danger of the crane twisting. By controlling the speed of the driving wheels with governing means, influenced only by the front control means, a suitable stabilizing feed-back mechanism is easily achieved, so that the crane frame, independent of the travelling direction, always quickly receives a very definite angular and side position in relation to the rail guiding the control member. When a separate guide-rail is used, the arrangement is such that an easily adjustable rail steers the travelling of the crane frame. It is not then necessary to adjust the track rails very exactly, as small bends or differences in the distance between them do not impede the travelling movement of the frame. In addition to this it is possible to steer the crane frame along a slightly bent track.

In the accompanying drawing the invention is shown applied on a crane arranged to travel on overhead rails. Figure 1 shows a travelling crane having a common track motor connected to the driving wheels in both girders by means of counter-shafts and Figure 2 shows a crane having separate driving motors for the driving wheels. Figure 3 is an enlarged section taken on the lines CC in Figures 1 and 2. This figure shows means which are sensitive to the position of a point in the front of a crane frame in relation to a rail.

In the figures, 1 is a crane frame having at each end two main end girders 2, connected by girders 3 and 4. Between the end girders 2 at each end of the frame there are two wheels 5 and 6 having no flanges, and horizontal guiding rollers 12 which are not normally in contact with the sides of the rails 20. The driving wheels 6 are connected to gears 7 in the crane and according to Figure 1, both the driving wheels 6 are connected to a common motor'9, which is mounted on a platform 11. Between the motor 9 and one of the wheels 6 there isa diiferential gear 16 mounted on the platform 18. The differential gear 16 is driven by a separate motor 17. Thecounter-shafts 13 and 14, connected to the driving motor 9, rotate with the same speed, but the shaft 15 arranged between the gear 7 and the diflerential gear i.e. differential gear 16, has a rotating speed which is higher or lower than the rotating speed of the shaft 14, when the motor 17 is rotating. In the crane according to Figure 2 the wheels 6 between the end girders, are driven by separate motors 8a and 8b, mounted on the platforms 10a and 10b respectively. In one of the end structures in the cranes control andgoverning means 19a and 19b are arranged. As shown in Figure 3, the control means comprise a shaft 33 slidably arranged in the brackets2'6, attached to the platform 21 at the lower side of the end girders 2. On the said shaft 33 there are two discs 32 which can rotate around the shaft, but are axially immovable on the shaft. The discs 32 are arranged on both sides'of one of the track rails 20, which rail is then also used as a guide. In the crane according to Figure 1, the rheostat influences the exciting circuit of the motor 17. In the crane according to Figure 2, the rheostats influence the exciting circuit of the two driving motors 8a and 8b. The conductors 29a and 29b and 30a and 30b connect the rheostats with the said motors.

The steering mechanism operates in the following way, when .the end girders, during the travelling of the crane frame along the track, change their position in relation to the rail 29, the discs '32 and the shaft 33 are moved sideways in the tracks 26. As a result of this movement of the shaft 33, the movable contacts 28a, 28b of the rheostats 27a, 2712 are moved and the field current of the driving motors 8a and 31) or the field-current of the motor 17 is influenced, and the speed of the driving wheels in one or both end girders is then increased or lowered. When the crane moves in the direction shown by the arrow A, the front control and governing means 19a steers the crane. When the crane moves in the direction' shown by the arrow B, the control and governing means 1% is in'the front and is then steering. Whichever of the control and governing members 19a and 19b is in'the frontof the frame, is connected to the'field circuitof the motors by a member not shown in the figure. When the crane changes its position in relation tothetrack the members 19a and 19b are actuated. When the crane moves in the direction shown by the arrow A and the front part of its right end girders are to the right, the contacts 28a, 28b of the rheostats 27a, 27b are moved to the left in relation toresistance coils on the brackets 25. The driving motor or the motor 17 is. then influenced in such a way thatvthe driving wheel in the right end, girder is given a higher rotation speed a lower speed. "By this method the crane frame will get the required angular and sideways position in relation to the guiding rail.

The invention is of course-not limited to the embodiment shown in the drawings, the speed of the driving wheels may-also be changed in other ways. It is only essential that the controland governing means which are located in the front of the crane frame influence the speed of .the driving wheels.

I claim as my invention:

1. A crane mounted to travel on track rails and comprising a rigid framework having integral end portions, driving wheels mounted'in said end portions and engaging the track rails, driving means for rotating the driving wheels in said end portions to move the crane along the said tracks, governingfneans connected to said driving means for changing the speed of the wheels in one ofthe end portions of the framework in relation to the speed of the wheels in the other end portion, two control means each connected to said governing means for controlling the operation of the same and arranged on both sides of the center line of the framework perpendicular to the track and each cooperating with one of said rails, said control means being sensitive to sideward movement of said framework in relation to said rails, said driving means being influenced only by the governing means connected to that one of said control means which is mounted at the forward side of the framework in relation to the direction of travel of the crane.

2. A crane according to claim 1, in which the said driving means includes a driving motor, means including a gear mechanism by which rotary motion from said motor is transmitted to the driving wheel in one of the said end portions operatively connecting said motor to said driving wheel, means including a differential gear through which the driving wheel in the other end portion is driven from said motor operatively connecting said motor and said other driving wheel, said governing means comprising a second motor connected to said differential gear to control the relative speeds of the driving wheels in said end portions. 7

3. A crane according to claim 1, in which the said driving means includes two separate motors carried by said crane each of which is operatively connected to both said control means and each of which is operatively connected to and arranged to transmit rotary motion to one of said driving wheels in the end portions of the crane.

References Cited in the file of this patent UNITED STATES PATENTS 2,556,503 Nelson June 21, 1951 

